Cyclooxygenases-1 and -2 (COX-1 and COX-2) catalyze the committed step in the conversion of arachidonic[unreadable] acid to prostaglandins (PGs) and thromboxane. COX-1 is constitutively expressed in many tissues and[unreadable] appears to play a role in homeostatic functions whereas COX-2 is highly regulated in response to a range of[unreadable] agonists and appears to contribute to pathophysiological responses. Selective inhibition of COX-2 has been[unreadable] exploited for the development of anti-inflammatory compounds with reduced gastrointestinal toxicities.[unreadable] However, the recent recognition of cardiovascular toxicity associated with the clinical use of these agents[unreadable] suggests that the role of COX-2 in normal physiology has not been fully appreciated. The major functional[unreadable] differences between COX-1 and COX-2 have primarily been attributed to their differential expression.[unreadable] However, we have shown that COX-2 is able to oxygenate a range of neutral derivatives of arachidonic[unreadable] acids, including the endocannabinoid, 2-arachidonylglycerol (2-AG). COX-2-dependent oxygenation of 2-AG[unreadable] leads to the formation of a range of glyceryl esters of PGs (PG-Gs) that is nearly as diverse as the PGs[unreadable] themselves. PG-G formation occurs in macrophage populations responding to inflammatory stimuli, and[unreadable] PGE2-G induces Ca2+ mobilization in RAW264.7 cells, supporting the hypothesis that PG-Gs represent a[unreadable] new class of lipid mediators. Here we propose to further exploit the resources of the Research Center for[unreadable] Pharmacology and Drug Toxicology to answer key remaining questions concerning the possible[unreadable] physiological roles of PG-Gs in vivo. We will 1) apply lipidomics and RNAi technology to monitor total lipid[unreadable] changes in macrophages during PG-G synthesis in order to identify the lipid pools that give rise to 2-AG and[unreadable] the specific enzymes that regulate 2-AG formation. 2) perform detailed kinetic studies of the interaction of[unreadable] hydroperoxy glyceryl esters with COX-2 in order to determine if PGG2-G, the immediate product of COX-2[unreadable] oxygenation of 2-AG, differs from PGG2 in its ability to activate or inactivate the enzyme; 3) characterize PGG[unreadable] formation by rabbit renal medullary interstitial cells, which appear to be a potential source of large[unreadable] quantities of PG-Gs that may be important in the regulation of renal function under hypertonic conditions; 4)[unreadable] characterize PGE2-G metabolism in the monkey in vivo to identify unique metabolites of PG-Gs that can be[unreadable] used to quantify in vivo biosynthesis of these compounds in humans. These experiments will provide critical[unreadable] information toward the development of a better understanding of the role of PG-Gs in vivo, and will help test[unreadable] the hypothesis that PG-G synthesis represents a unique physiologic function of COX-2.